Thermally stable polyphosphonates as flame retardants

ABSTRACT

A thermally stable flame-resistant phosphonate polymer of the structure   WHEREIN R1 is methyl or ethyl, R2 is hydrogen or methyl and n is 3 to 100, is formed by the reaction of acrylic or methacrylic acid with an alkyl bicyclic phosphite of the structure   WHEREIN R1 is as above. The phosphonate polymer is useful in forming flame-resistant acrylic compositions such as molding powders and sheets from mixtures comprising the polymer and methyl methacrylate.

Uited Sttes Patet 1 Clovis et a1.

[ Aug. 28, 1973 THERMALLY STABLE POLYPHOSPHONATES AS FLAME RETARDANTS[75] Inventors: James S. Clovis; Francis R. Sullivan,

both of Warminster, Pa.

[52] US. Cl 260/80 P, 252/8.1, 260/2 P,

260/80 PS, 260/876 R, 260/937, 260/DIG. 24 [51] Int. Cl. C08f 3/42, C08g17/133 [58] Field of Search 260/80 PS, 2 P, 937

[56] References Cited UNITED STATES PATENTS 11/1964 Emmons ..260/80.7111/1964 Emmons ..260/461 Primary Examiner-Joseph L. Schofer AssistantExaminer-C. A. Henderson Attorney--W. F. Simmons et a1.

[57] ABSTRACT A thermally stable flame-resistant phosphonate polymer ofthe structure wherein R is methyl or ethyl, R is hydrogen or methyl andn is 3 to 100, is formed by the reaction of acrylic or methacrylic acidwith an alkyl bicyclic phosphite of the structure wherein R is as above.The phosphonate polymer is useful in forming flame-resistant acryliccompositions such as molding powders and sheets from mixtures comprisingthe polymer and methyl methacrylate.

3 Claims, No Drawings THERMALLY STABLE POLYPHOSPHONATES AS with an alkylbicyclic phosphite of the structure FLAME RETARDANTS The presentinvention relates to a novel thermally CHPO stable phosphonate polymer,to a process for making this polymer and to acrylic compositions such asmolding powders and sheets of superior flame-resistant properties. Theacrylic compositions comprise an addition polymer formed from a mixturecontaining the novel phosphonate Compounds wherein R is as defined asabove. The alkyl bicyclic Hechcnbleiker et 3.1., Pat. No. issuedphosphite in tum may be formed the reaction of May 13, 1958 Shows cyclicOrganic P P phosphorous trichloride with a trimethylolalkane such Poundsbased on the P P g Y5 as trimethylolpropane. See Emmons et al., U.S.Pat. tern useful as plasticizers and stabilizers for vinyl chlo- 3 155703 issued 1 3 4 ride resins and other plastics or as intermediates forThe reaction between the phosphite and acrylic or forming othercompoundsoiBrlen 6t methacrylic acid is preferably carried out in polarsol- 2,934,555 issued P 1960, teaches p y vents such as methylenedichloride, ethylene dichloride able acrylic 0r methacrylic est rs ofalkyl hydr xyalkylor tetrachloroethane. An exotherm occurs during thephosphonates useful as monomers for polymerization reaction and is bestcontrolled by agradual addition of and copolymerization with otheracrylic esters to yield the acid to the solution of the phosphite inrefluxing flame-resistant plastics, coating, textile finishes, etc.solvent. The course of the reaction is followed by the Forsyth, U.S.Pat. No. 3,468,980; issued Sept. 23, decrease in acid number andincrease in solution vis- 1969, teaches flame-retardant phosphonatepolymers cosity. characterized by the unit v The structure of theproduct of the reaction between acrylic or methacrylic acid with acyclic phosphite is difficult to predict. The expected route for polymerformation would first involve addition of the bicyclic 2 0DCl/..phosphite to the double bond of the a, B-unsaturated acid. The resultingzwitterion would undergo proton wherein R and R each contains up to 12carbon atoms exchange to give (I). and represents alkyl, phenyl,phenylalkyl, alkylphenyl, alkenyl and alkoxycarbonyl. R and R takencollectively with the carbon atom to which they are attached, 0 form analiphatic ring of 5 to 7 carbon atoms. Thls al i- R P+ CH2 (I:H CO2phatlc ring may be saturated or monounsaturated. It is preferred thatthe total number of carbon atoms in R 0 (t) plus R be no greater than17. D represents an alkylene Polymer would form by participation of thetwo molgroup of 2 to 3 carbon atoms or the alkyl-substituted ecules of lin an intermolecular Arbusov rearrangealkylene group wherein thealkylene portion contains ment.

2 to 3 carbon atoms and the alkyl substituents total up The expectedroute does not agree with the observato 8 carbon atoms. The polymers areuseful for forming tions that the phosphite-acid reaction solution ofthis flame-resistant acrylic sheets. invention shows a strong alcoholic-OH and often an The present invention relates to a thermally stableanhydride peak at 5.5p.. it is thought, although appliflame-resistantphosphonate polymer characterized by cants do not intend to be bound bythis explanation that the structure the following reaction sequenceoccurs.

Me f f t o-i':c=orr I ammo-co n R 'O 1 R on cr og (or 11 EE n 0 o Y a \rI! -CIICR POHZCIIRECO- 0 z-O n R-C P R1 Q 111 wherein R is methyl orethyl, R is hydrogen or methyl ocfi c1{ c 1-I C o-cc=CII: and n is 3 to100. This flame-resistant polymer is formed by the reaction of acrylicor methacrylic acid (III) IIOHzC The acrylic composition of the presentinvention comprises an addition polymer formed from a mixturecomprising; (a) at least 50 percent by weight of methyl methacrylate,and (b) S to 30 percent by weight of a flame-resistant phosphonatepolymer defined by the general formula given supra. The mixture mayadditionally comprise 5 to weight percent of a member selected from theclass consisting of isobomyl acrylate, isobornyl methacrylate andmixtures thereof and/or up to weight percent of an ethylenicallyunsaturated acrylic compound such as acrylic or methacrylic acids. Theacrylic compositions of this invention may be formed by any processknown in the art such as for example those referred to and shown inForsyth, US. Pat. application, Ser. No. 819,484, filed Apr. 25, 1969,now U. S. Pat. No. 3,634,554 of Jan. ll, I972.

Theaddition polymer may constitute the entire body of the composition orit may, for example, constitute the main body and serve as a binder insheet form for common additives such as coloring dyes or pigments,release agents and other additives.

It is particularly notable that the phosphonate compositions of thepresent invention exhibit excellent thermal stability. This property isof particular importance where the compositions are to be incorporatedinto molding powders for processing by extrusion and molding operations.Commonly used commercial flame-retardant phosphonate compositions suchas that prepared from ethylene chlorophosphite and acetone and thatprepared from acetaldehyde, ethylene oxide and PCl are not stable aboveabout 180 C. while common processing temperatures for molding powdersare near 250 to 275 C. The phosphonate compositions of the presentinvention are advantageously thermally stable at these processingtemperatures.

A preferred embodiment of this invention is an acrylic composition, themain body of which is an addition polymer formed from a mixturecomprising (a) at least 50 weight percent methyl methacrylate, (b) 10 toweight percent of the flame retardant, and (c) 4 to 8 weight percentmethacrylic acid or acrylic acid.

The class of other ethylenically unsaturated acrylic monomers useable inquantities up to 25 weight percent includes monoethylenicallyunsaturated acrylic compounds and polyethylenically unsaturated acryliccompounds. The unsaturated acrylic compounds constitute a class ofcompounds known in the art and include but are not limited to suchcompounds as methacrylic acid, acrylic acid, alkyl esters andsubstituted alkyl esters of acrylic acid and methacrylic acids, such asethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isobutylacrylate, isobutyl methacrylate, ethylthioethyl methacrylate oracrylate, isobutyl acrylate, halogenated alkyl methacrylate, glycidylmethacrylate and the like; and dior polyacrylic esters of diols andpolyols, such as l,3-butylene dimethacrylate, 1,3-butylene diacrylate,trimethylolpropane trimethacrylate and the like; acrylic nitriles, suchas acrylonitrile, methacrylonitrile and the like. The inclusion of theseethylenically unsaturated acrylic compounds offers specialcharacteristics that are particularly useful in some end-useapplications. The inclusion of these compounds may improve 0 0 physicalproperties including the heat distortion temperature and clarity. Asexamples, acrylic esters or polyethylenically unsaturated acrylicmonomers may be utilized to improve high temperature heat resistance andother physical properties. Generally, the concentrations of thepolyethylenically unsaturated monomers are maintained at a low level toallow thermoforming of the sheet or injection molding of moldingpowders. The ethylenically unsaturated acrylic monomers may be a mixtureof two or more of the compounds from the class. The variation of theinvention by including these ethylenically unsaturated acrylic monomersis within the gamut of this invention.

To assist those skilled in the art in the practice of the presentinvention, the following modes of operation are set forth asillustrations, parts and percentages being by weight unless otherwisespecifically noted.

EXAMPLE I The example illustrates the preparation of the alkyl bicyclicphosphite. A slurry of I34 g. of trimethylolpropane (1.0 M) in H5 g. ofethylene dichloride is brought to reflux at a pressure of ca. I00 mm. toazeotrope off any water present. The reaction mixture is then cooled to15 C. To the cooled and stirred solution which is kept under nitrogen isadded dropwise 140 g. of PCl (1.02 M) over a 3-hour period. The reactionmixture is stirred overnight at room temperature after which time thesolution is gradually heated to C. and refluxed under vacuum (ca. 50mm.) until the acid number is less than two. An IR spectrum of thesolution is taken to insure the complete reaction of the -CH OH groups.The distilled yield of phosphite is about percent, which agrees wellwith the 92-98% solution yields obtained from bromine numberdeterminations.

EXAMPLE 2 This example illustrates the preparation of the flameresistantphosphonate polymer of the present inventlOn.

To the solution described above is added ca. 60 g. of ethylenedichloride (EDC) and 2.34 g. of acetic anhydride (0.5 wt. of finalreaction solution). The solution is brought to reflux for A hour and ismaintained under a nitrogen atmosphere. Seventy-two grams (1.0 M) offreshly distilled acrylic acid containing'2.34 g. of acetic anhydride isadded over molecular sieves to the refluxing solution during a 4-hourperiod. The addition funnel is washed down with 20-25 ml. of EDC. Thereaction solution is maintained under reflux for an additional 2 hours.The final solution acid number is between 25-35.

The product is recovered by stripping off the volatiles under vacuum inthe presence of 1 percent benzyl chloride (by weight on solids) atl70-l80 C. Alternatively, the product may be recovered by precipitationinto ether. The product is a colorless to yellow solid with a softeningpoint of 80-90 C. The yield is ca. 70 percent (precipitation) to about95 percent (stripping).

Characterization of the product by elemental analysis, infrared spectraand unsaturation by bromine number indicates a product consistant with apolymer characterized by the strucure wherein n varies form 3 todepending upon the method of recovery. The product is characterized byexcellent thermal stability.

EXAMPLE 3 This example illustrates the preparation of acrylic sheetmaterial of the present invention.

Fifteen grams of the product obtained from Example 2 is dissolved in 80g. of methyl methacrylate and 5 g. of glacial methacrylic acid to whichhas been added 0.03 grams of a 25 percent solution of acetyl peroxide indimethyl phthalate. The resulting solution is polymerized between glassplates. The resulting sheet has a self extinguishing rating by ASTMD63556T.

EXAMPLE 4 This example illustrates the preparation of the acrylicmolding powder of the present invention.

Fifteen grams of the product obtained from Example 3 is dry blended with85 g. of a copolymer of methyl methacrylate/methacrylic acid/ethylacrylate; 92.1/5.9/2.0, -=08. The resulting blend is extruded intopellets which are injection molded into bars which are SE 11 by test UL94.

EXAMPLE 5 This example shows the improved thermal stability of thepolymers of the present invention.

The following table shows weight loss and Acid Number change for samplesof the flame-resistant phosphonate polymer prepared in Example 2, heatedat 180 C. and at 200 C.

TABLE Temp. Time Weight Loss Acid C. Minutes Percent Color Number Yellow30 180 30 2.2 Yellow 33 180 60 2.5 Yellow 33 200 30 1.5 Yellow 33 200 601.8 Yellow 30 200 2.0 Light Amber Gel wherein R is methyl or ethyl, R ishydrogen or methyl and n is 3 to 100.

2. The polymer of claim 1 wherein R is ethyl and R is hydrogen.

3. A process for preparing a flame-resistant phosphonate polymercomprising reacting acrylic or methacrylic acid with an alkyl bicyclicphosphite of the structure wherein R is as defined in claim 1.

I INITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.,3,755,270 Dated August '28, 1973 I nventor(s) James S. Clovis andFrancis R. Sullivan It is certified that error appears in theabove-identified pater It and that said Letters Patent are herebycorrected as shown below:

IN THE SPECIFICATION:

Column 2, structure in line 35 should have a bond (econnecting line)between the "middle 0" and the "P" to complete the bicyclic structure.

The same is true for the structure on lines I-O and 55,

. ?1 v Rf O P CH CHCO should be R P CH 0 H-CO Signed and sealed this31st day of December 1974.

(SEAL) Attest:

WcCOY 2i. "GIBSON JR. 1 C. IMRSHALL DANN Attesting. Officer Commissionerof Patents USCOMM-OC 60376-P69 us GOVERNMENT Pnmmqe ornc: u 0-366-334,

FORM 1 2085 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patentNo. 3,755,270 Dated August 28, 1973 1 r( Jemes S. Clovis and Francis R.Sullivan It is certified that error appears in the above-identifiedpatent and that said Letters Patentare hereby corrected as shown below:

IN THE SPECIFICATION:

Column 2, structure in line 35 should have a bond (a connecting line)between the "middle O"-and the P" to complete the bicyclic structure.

The same is true for the structure on lines +O and 55.

B- O P CH CHCO should be 0 R1 R PCH CH--CO Signed and sealed this 31stday of December 1974.

(SEAL) Attest:

McCOY I-I. GIBSON JR. C. I'iARSHALL DANN Attesting Officer Commissionerof Patents USCOMM-DC 60376-P69 1M 2085 v I v 0.5 eovznuuam mumus omc: uo-ase-au.

2. The polymer of claim 1 wherein R1 is ethyl and R2 is hydrogen.
 3. Aprocess for preparing a flame-resistant phosphonate polymer comprisingreacting acrylic or methacrylic acid with an alkyl bicyclic phosphite ofthe structure